Integrated circuits are manufactured from crystalline wafers, typically silicon wafers. These wafers are subjected to numerous processing steps in highly controlled environmental conditions. The wafers are extremely fragile and vulnerable to damage and contamination. The wafers are typically round in shape and are transported, stored, and processed in wafer carriers of various types. Wafer carriers are typically formed of plastic and will generally have a machine interface that provides precise positioning of the wafer carrier on equipment. A common wafer carrier utilized in semiconductor fabrication facilities is the H-bar wafer carrier. This carrier has an open front, or top depending on the orientation, a pair of sidewalls, and a pair of endwalls. One of the endwalls has an H-bar machine interface. Wafers are inserted and withdrawn through the open front from a plurality of slots defined by recesses on the inside of the carrier sidewalls. The recesses are defined by projections extending generally toward the opposite sidewall. The projections may be configured as teeth. For conventional wafers the carriers typically support and restrain the wafers at their peripheral edges.
Conventional wafers are 0.030 inches thick. As industry has striven to make electronic devices smaller, integrated circuits have become denser, smaller, and thinner. Integrated circuits are now being manufactured from thin wafers having a thickness of 0.007 in.
Robotic means are generally utilized for handling and processing of the individual silicon wafers into the integrated circuit chips including the insertion and withdrawal of the wafers from carriers. Intermediate processing steps the wafers are typically supported in H-bar wafer carriers and individual wafers are withdrawn and inserted by transfer equipment with robotic arms. The set up of the transfer equipment is highly critical so that the wafers are properly grasped and not damaged during any such transfers. To the extent possible, for economic reasons, it is desirable to utilize the same processing equipment and the same setup for the transfer equipment, when then wafers are utilized as opposed to be conventional wafers.
Generally semiconductor fabrication facilities are now being set up for 200 or 300 mm wafers. In that the thin wafers are substantially more fragile and less rigid than the conventional wafers, when such wafers are peripherally supported in conventional wafer carriers, the wafers bow downwardly in the middle of the wafer due into gravity. This requires modification of the wafer transfer equipment to accommodate said bowing and prevent damage to the wafer. It would be desirable to be able to utilize conventional wafer carriers such as H-bar wafer carriers and not have to reconfigure the transfer equipment when thin wafers are being processed.